Not Zensors, but I like to apply about 1-2db lower treble on my Spektors as they can be slightly sharp w/some material/sounds.
No expert here, but I suspect the sligth load dependency of the Fosi might aggravate the treble response somewhat? I found that to be the case also with my Argon SA1 amp.
I also have some measurements from my room, with a Powernode N330, where I had the speakers front firing vs toed in. You can see the toed in response gets brigther with the curve in purple. For full disclosure I also had treble +1db in this measurement. Still, there would be about 3db difference if the EQ were set to neutral.
So at least ensure the speakers are firing straight ahead.
Edit: I mixed the curves in this post - they are actually showing toe in (purple) and with -2db/firing straight ahead (green). Later post also updated with better scale.
After changing to the Powernode, I have not noticed much if the sharpness, even w/o EQ.